Implements, such as tools, weapons, and the like, may be temporarily encased in a carrier (such as a holster, for instance) for protection of the implement and/or the user, while providing access to the implement. For example, a carrier may allow a user to conveniently carry the implement, safely retaining the implement until needed. When the implement is to be used, the user may withdraw the implement from the carrier, and then return it to the carrier when finished. In some cases, such as with a handgun for example, the holster may allow the user to conceal the implement, or to conceal the fact that the user is carrying the implement.
In the case of a handgun, the holster should reasonably protect the handgun and the user, and should be convenient to the user for ready use. However, the holster should also be versatile enough to be comfortably carried by the user, such as when it is worn on the person of the user for an extended length of time. The holster should also be rigid and stable enough to allow the handgun to be repeatedly drawn and re-holstered, usually with the same hand.
A holster should reliably retain the handgun until it is to be used, but allow the user to draw the handgun for use without undue effort or difficulty. It may be desirable to adjust the retention of a holster, to accommodate the user's preference and intended type of use. In some cases, adjusting the retention of holsters, and particularly adjusting the retention of hard shell holsters can be problematic.